On the Motion Law of the Sun and Venus

On the afternoon of June 8, 2004, astronomy enthusiasts from all over the world were very excited to observe the beautiful transit of venus for the first time. This is the sixth time that human beings have observed this rare astronomical phenomenon of transit of venus. The last time it happened at the end of 19, that is, 105 and a half years ago.

"Sister" of the Earth-Venus

Among the nine planets in the solar system, Venus is the most familiar planet except the Earth. Venus was called Taibai in ancient China. When it appears in the East in the morning, it is also called Qi Ming, Xiaoxing and Xingxing. When it appears in the west in the evening, it is also called Chang Geng and Twilight.

Venus is the brightest celestial body in the sky except the sun and the moon. The brightest apparent magnitude can reach -4.4, which is more than ten thousand times brighter than the darkest star that people can see with normal vision (about 6) 1 10,000. On the one hand, Venus is very close to the sun, with an average distance of only 1. 1 100 million kilometers, and it receives more solar light than the earth 1 times. On the other hand, there are thick light-colored clouds around Venus, and the albedo is as high as 0.76 (the albedo of the earth and the moon are 0.39 and 0.07 respectively). If the albedo of the moon is as high as that of Venus, then people can read books and newspapers effortlessly under the full moon. Venus is very similar to the earth in size, mass, density and internal structure. Venus has a radius of 6050 kilometers, only 4% smaller than the earth; The mass is 4.9× 1024 kg, which is about 20% smaller than that of the earth. The average density is 5.26 g/cm3, which is only 5% lower than that of the earth. Venus has an iron-nickel core with a radius of 365,438+000 kilometers, with a "mantle" mainly composed of silicon, oxygen, iron, magnesium and other compounds in the middle, and a very thin "shell" mainly composed of silicon compounds on the outermost surface, which is very similar to the earth. For this reason, Venus is called the "twin sister" of the earth. Venus and Mercury are the only two big planets in the solar system without natural satellites. Among the nine planets, Mercury is closest to the sun (with an average distance of 58 million kilometers), followed by Venus.

However, Venus is very different from the Earth in its motion characteristics. First of all, the rotation speed of Venus on the equator is only 1.8 m/s, and it takes 243 days to rotate once. Moreover, Venus rotates from east to west, which is opposite to the rotation direction of other planets in the solar system except Uranus. Therefore, on Venus, the sun seems to rise in the west and set in the east. Venus takes about 224.7 days to orbit the sun, and its rotation period is longer than that of period of revolution. However, because the rotation direction of Venus is opposite to that of its revolution, a day and night on Venus is approximately equivalent to 1 17 days on Earth. Watching the sunrise on Venus requires special patience. It takes at least 6 hours for the sun to shine from the horizon of Venus to be completely exposed to the ground, while in the mid-latitude region of the earth, this process usually takes more than 3 minutes.

Venus's atmospheric density is 100 times higher than that of the earth, and its clouds are tens of kilometers thick. The main component of the atmosphere is carbon dioxide, and the atmospheric pressure exceeds 9× 106 Pa. The surface temperature of Venus is as high as 475℃, and lead can be melted at this temperature. Due to the greenhouse effect of carbon dioxide atmosphere, there is no temperature difference between day and night on Venus, and there is no seasonal change of hot and cold. In view of such "bad" conditions, there can be no life on Venus. As far as the topography of the surface of Venus is concerned, it is relatively flat because of the protection of a strong atmosphere, unlike many crater structures of the moon, mercury and Mars. There are mountains on Venus, and volcanoes can reach hundreds of kilometers in diameter.

In astronomy, the planets within the Earth's orbit (namely Venus and Mercury) are collectively called inner planets, while the planets outside the Earth's orbit (namely Mars, Jupiter, Saturn, Uranus, Neptune and Pluto) are called outer planets. From the earth's point of view, the position of the planet on the earth is always hovering near the sun. Venus (and mercury) sometimes rises before the sun and appears on the eastern horizon at dawn, which is called the "morning star"; Sometimes it appears at the low altitude in the west in the evening after sunset, which is called "the evening star". When Venus is farthest away from the sun in the sky, the angular distance between Venus and the sun can reach 48, while when Mercury is far away from the sun, the angular distance between Venus and the sun does not exceed 28, so Mercury is often hidden in the sunlight and is not easy to be observed.

Venus, as an inner planet, has obvious phase changes like the moon, that is, at different times, because of the different relative positions of the earth and Venus, the shape and size of Venus are also different; However, because Venus is far away from the Earth, the naked eye cannot find this change. When the moon phase changes, the diameter of the moon surface does not change obviously, but Venus looks the largest at the new moon, because it is closest to the earth at this time, about 40 million kilometers; It is very small when it is close to the circle, and the difference between them can reach more than 6 times. At this time, Venus is more than 250 million kilometers away from the Earth. In A.D. 16 10, Galileo first observed Venus through a telescope, and discovered the phase and size changes of Venus, which became strong evidence for Copernicus and Heliocentrism.

The history of Venus space exploration

Man's space exploration of planets of the solar system began with Venus. On the one hand, Venus is the main celestial body closest to the Earth in the solar system except the moon; On the other hand, the surface of Venus is surrounded by thick clouds, and people must carry out close-range field exploration if they want to see its true face. 1957 Shortly after the launch of the first artificial satellite, the Soviet Union and the United States began to explore Venus in space after the 1960s. So far, more than 40 probes have been sent to or passed through Venus, and many valuable scientific information about Venus has been obtained.

The Soviet Union took the lead in exploring Venus in space. From 196 1- 1969, the probes "Giant" and "Venus 1" were launched successively to "Venus 6", but the surface of Venus could not be detected for various reasons. 1970 17 In August, Venus 7 made its first soft landing on the surface of Venus, and measured the surface temperature and atmospheric pressure of Venus. 1972 "Venus 8" reached the surface of Venus, tested the soil, and televised the intensity of sunlight and clouds.

The period from 1975 to 1984 was the climax of the Soviet Union's exploration of Venus, and eight probes from Venus 9 to Venus 16 were launched. "Venus 9" and "Venus 10" arrived at Venus on June 1975+00, becoming two satellites of Venus. /kloc-0 "Venus 1 1" and "Venus 12" launched successively in September, 1978 successfully achieved a soft landing; Venus 13 and Venus 14 launched in June 198 1 and June1respectively drilled the surface of Venus and collected rock samples. 1983 was launched in June, and "Venus 15" and "Venus 16" arrived in Venus in June of the same year and became satellites of Venus. These two probes orbit Venus once every 24 hours, and successfully draw the topographic map of Venus with the resolution of 1 ~ 2 km. The Venus-Harley probe launched in February 1984 joined Venus in June of the following year, and released the helium-filled balloon and landing module to detect and analyze the clouds and soil of Venus. After completing a series of visits to Venus, the probe used the gravity of Venus to change its orbit and flew to Comet Halley.

In the case that space exploration lags behind the Soviet Union, on the one hand, the United States fully implements the moon landing program, on the other hand, it actively explores Venus. 1961On July 22nd, the United States launched Mariner 1, but it deviated from the original orbit shortly after launch and had to blow itself up. Mariner 2,1launched on August 27th, 962,1flew over Venus for 3500 kilometers on February 24th, 962. Although some instruments failed, it measured the temperature of Venus' atmosphere for the first time and took a panoramic picture of Venus. Later "Mariner 5", "Mariner 10" and several "Pioneer-Venus" explorations were successful. Some of them became satellites of Venus, studied the atmosphere and surface magnetic field of Venus, and some released the landing module, inspected the topography of Venus in many aspects, and sent back a lot of precious pictures and data.

The most noteworthy thing in the Venus space exploration program is the Magellan probe, which was launched by the American space shuttle Atlantis on1May 4, 989. The detector weighs 3365 kg and costs 4130,000 USD. After a flight of 15 months, it reached Venus on August 1990 and became a satellite of Venus the next day. Magellan probe used advanced radar detection technology to survey the whole picture and geological structure of Venus in detail, including shooting and drawing a large number of clear photos and images on the surface of Venus, and found many volcanoes, lava flows, crustal faults, craters and so on. And measure the activity, composition, surface temperature and magnetic field of Venus atmosphere. After more than four years' work, the Magellan probe was burned in the atmosphere of Venus in June 5438+0994+1February, which was a great success.

Although the focus of planets of the solar system's exploration has recently shifted to Mars, the space exploration of Venus has not stopped. Japan plans to launch a Venus probe in 2007 and is expected to reach Venus in 2009. The probe will carry five special infrared cameras and ultraviolet cameras, which can penetrate the atmosphere of Venus and detect the atmosphere and geological structure of Venus.

Transit of venus's Principles and Laws

When the moon moves between the earth and the sun and is in a straight line with the earth and the sun, the shadow of the moon will sweep across the surface of the earth, and annular eclipses can be observed in some areas of the earth. To an observer on the ground, an eclipse looks like the moon is covering the sun. The moon covers all the sun, which is a total solar eclipse; Only a part of the sun is covered, which is called a partial solar eclipse.

The principle of transit is essentially the same as that of solar eclipse. Planets on the earth (that is, mercury and venus) sometimes lie between the earth and the sun during their movement. When they are in a straight line with the earth and the sun, the transit phenomenon will occur. Although Venus and Mercury are bigger than the moon, they are far away from the earth and look much smaller than the moon on the earth, so when the transit occurs, observers on the earth can only see a small black dot moving slowly on the surface of the sun. Transits only occur on the planets of the earth, so there are only two kinds of transits: Mercury transits and transit of venus.

The orbital plane of the earth around the sun is called the ecliptic plane. Only when the local planet is located between the earth and the sun, and its orbital plane intersects with the ecliptic plane, will the transit occur. Therefore, the appearance of transit phenomenon is very regular. The transit of mercury must occur around165438+1October 18 or May 8, with an average of 13 times every 100, of which165438+/kloc-0.

The closer you are to the sun, the greater the chance of a transit. Venus is farther away from the sun than mercury, so the chance of transit is much smaller than mercury. Transit of venus is bound to happen around June 7th or February 9th of 12, and there is a little more chance of transit around June 7th. Venus orbits the sun in period of revolution for 224.705438+0 days, and the earth in period of revolution for 365.246 days, so the rendezvous period between them is 583.92 days. Generally speaking, the interval between two transits is 8 years, 105.5 years, 8 years,1210.5 years, and this cycle is 243 years, which is also the most basic and stable cycle in transit of venus. In 243 years, it may happen five times in transit of venus. Strictly speaking, transit of venus has cycles of 8 years, 243 years and 25 1 year. The 8-year period is equivalent to 8 Earth years, 13 Venus years and 5 rendezvous periods, the 243-year period is equivalent to 243 Earth years, 395 Venus years and 152 rendezvous periods, and the 25 1 year period is equivalent to 25 1 Earth years, 408 Venus years and/. But the specific situation is more complicated. If the path of Venus in the last transit just passed near the center of the sun's circular surface, the path of Venus will be just outside the edge of the sun's circular surface after 8 years, so there will be no two consecutive transits of Venus after 8 years.

The Observation History of transit of venus

Man's observation of Venus can be traced back to a long time ago. Around 3000 BC, the Babylonians observed Venus. /kloc-in the 7th century, Kepler predicted for the first time on the basis of Heliocentrism that transit of venus would occur in 163 1 year. However, since the transit is invisible in Europe, no one has witnessed this phenomenon, and Kepler himself failed to predict that the transit of venus phenomenon will reappear on 1639 eight years later.

People first saw transit of venus in 1639, and it was an Englishman J. horrocks who predicted transit of venus. Although he never received a formal astronomy education, he accurately predicted1639165438+1transit of venus on October 24th by observing the planets such as Venus and the sun for many years, and observed the whole process of Venus passing slowly on the circular surface of the sun, thus becoming the first person in history to predict and successfully observe the transit of venus phenomenon.

After observing the transit of Mercury in 1677, Harley realized that the distance between the sun and the earth could be measured by transit of venus, and predicted the transit of venus in 176 1 year. 176 1 On June 6th, astronomers observed transit of venus according to the suitable observation points predicted by Harley. The observation data of about 70 points confirmed Harley's prediction, and accurately determined the distance from the earth to the sun for the first time, that is, the length of astronomical units. However, due to the unsatisfactory weather conditions at some observation points, astronomers could not accurately measure the longitude of the observation points at that time, and Harley's calculation was not perfect, so transit of venus could not be seen at some observation points he expected.

On June 3rd, transit of venus 1769 can only be seen in the Pacific Ocean and western North America. A total of 15 1 observers observed at 77 points, and many astronomy enthusiasts participated. Captain J Cook observed this rare astronomical phenomenon in Tahiti, South Pacific, and all the observations were very successful. Transit of venus occurred twice in19th century, namely1February 9th, 874 and1February 6th, 882. The United States Congress allocated175,000 dollars and $85,000 dollars for observation activities respectively. In the whole 100 year of the 20th century, there was not a transit of venus. In human history, including the transit on June 8, 2004, there were six astronomical phenomena in transit of venus, so it can be said that the transit of venus phenomenon is rare.

Transit of venus's observation content

The whole process of transit of venus depends on the trajectory of transit of venus time. The closer the path is to the center of the sun's circular surface, the longer the transit process. During the transit in 2004, the whole process lasted more than six hours. There are five special moments in the transit of venus process: when Venus is tangent to the sun, it is called the transit tangent, which marks the beginning of the transit process; When the Venus circle is inscribed with the Sun circle, it is called Lingshi inscribed. From this time on, the entire Venus circle entered the solar circle. The moment when the center of Venus is closest to the center of the sun is called Chen Ling, which has no special significance in transit. When the Venus circle and the sun circle are inscribed again, it is called the final circle; Finally, the round surface of Venus and the round surface of the sun are circumscribed again, which is called the terminal tangent plane. In these five special moments, it is impossible to directly obtain the moment of Ling, and it is also difficult to record the moment of Ling's circumscribed. What can be recorded more accurately are Ling's internal cutting, Ling's internal cutting and Ling's external cutting. After ling finally cut it out, he couldn't see Venus.

In transit of venus in 2004, it was favorable to observe in the western and northern areas of China, but in Shanghai, the sun had set before the end of the transit, so it was impossible to observe the internal and external cuts of the transit. In Shanghai, the time of stone forest external cutting is 13: 12: 13, and the time of stone forest internal cutting is 13:3 1:09. You can see the whole process of Beijing transit. The transit period is13:13:15-19:18: 53, but the position of the sun in the sky is already very low at the end of the transit. Although the weather in Shanghai on June 8 was not conducive to observation, astronomy enthusiasts and media reporters were still in high spirits and made full preparations. As a result, many things happen. At about 4 pm, after a heavy rain, it turned from partially cloudy to cloudy. Visual observation, photography, video recording and projection observation were all successful, and the observation work continued until the sun went down. The author is also fortunate to see this rare astronomical phenomenon. During this transit, Venus' running path on the surface of the sun starts from the lower left position of the sun and moves to the lower right. However, after about 3 hours of transit, that is, around 4 pm, the overall impression of the observer is that the whole trajectory is located on the left side of the center of the circular surface of the sun, and it moves from top to bottom. This is because the predicted Venus path map is set when the sun is due south, so the equatorial plane of the sun is almost parallel to the southern horizon, that is, in the positive east-west direction. But in fact, during the transit, due to the rotation of the earth, the sun moved westward from the position near the south, and it was located in the west around 4 pm. At this time, the angle between the equatorial plane of the sun and the western horizon becomes very large. Therefore, Venus moves from top to bottom on the surface of the sun.

Transit of venus is rare, but we must make full preparations in advance to successfully observe the transit phenomenon. First of all, we must pay attention to protecting our eyes. Never use ordinary sunglasses to observe the sun directly, and no matter what method you take, don't stare at the sun for a long time. In addition, it is best to use a special solar eclipse observation card, and carefully check whether the film layer of the observation card is intact before use. You can also use welded protective glass, ordinary glass completely blackened by smoke, and several layers of overexposed films to fully weaken the sunlight entering the eyes. If you observe with a telescope, you should pay attention to the telescope not facing the sun for a long time to protect the lens. At the same time, a filter coated with a highly reflective film must be added in front of the objective lens. Because of the strong sunlight, a telescope with a diameter of 5 ~ 6 cm is enough. In order to accurately determine the time when Venus is tangent to the sun, the magnification of the telescope should be 100 ~ 150 times. In addition to visual inspection, you can also observe by projection. Because Venus can't be seen before entering the solar circle, we must wait patiently for the appearance of the tangent of Venus' polar line according to the predicted polar line time and the position angle of Venus at that time.

In the process of transit of venus, we should try our best to observe two interesting phenomena: "black drop" and "halo". Both black drops and halos appear at the moment after entering Ling and before leaving Ling. The black drop effect is a phenomenon that the edge of Venus and the edge of the sun are "stuck" together by the shadow of oil drops when they are tangent to the surface of the sun during the transit of venus process, which is caused by the tranquility of the atmosphere, the diffraction of light and the limited resolution of the telescope. In the entry and exit stages, sometimes the edge of Venus' circular surface will be inlaid with a tiny halo or halo, which is formed by the reflection and scattering of solar light at the top of Venus' atmosphere.

Transit of venus 20 12

The next transit of venus will take place on June 6, 20 12. For most parts of China, including Shanghai and Beijing, the transit takes place in the morning, and people can see the whole process of the transit. The length of the whole process is almost the same as that in 2004, but in western China, the transit process has already started at sunrise (called "coming out with the transit"). Globally, the whole transit process can be seen in the northwest of North America, the western Pacific (including Hawaii), northern Asia, eastern and northern China, Japan, the Korean Peninsula, the Philippines, eastern Australia and New Zealand. In most parts of North America, the Caribbean and the northwest of South America, the transit process did not end at sunset (called "taking ice without ice"); Central Asia, the Middle East, Europe and East Africa are rising; The completely invisible areas are Portugal, southern Spain, West Africa and southeastern South America, which accounts for about two-thirds of South America.

The next few transit of venus events will take place in 2 1 17,1,2 125, 1 1 in June, 2247. Astronomers can accurately predict the solar eclipse, lunar eclipse and transit of venus in 1000 or even longer.

People have observed transit of venus for more than 300 years since 1639. Early astronomers measured the kilometers of astronomical units by observing this phenomenon. Today, people only look at transit of venus as a rare astronomical phenomenon, and the transit itself has little scientific research significance. However, this phenomenon provides an important way for astronomers to find planets of other stars outside the solar system. Because the star is very far away from the Earth, even if there are planets around it, it can't be directly observed with the current technology. We must use indirect methods, one of which is to observe the "Ling Xing" phenomenon. Because the planet revolves around the star, but the planet doesn't shine, when the planet around a distant star is between the star and the earth, it will block part of the star's starlight. This is the Ling Xing, and its principle is the same as the transit of planets on the earth. Seen from the earth, when Ling Xing occurs, the starlight of the star will be weakened, which can be observed from the earth. By analyzing the law of starlight attenuation in Ling Xing process, we can calculate the orbit and mass of the planet around the star. This method is called "Lingxing Method".

Only when the orbital plane of the planet around the star is consistent with the observer's line of sight on earth can the transit method be used to find the outer planet. So far, only one star's Ling Xing phenomenon has been observed, and it is found that the mass of the planets around it is 0.67 times that of Jupiter. In 2007, NASA will launch the first space probe "Kepler" to explore other planets. It will orbit the sun, and it is planned to explore 40,000 stars in four years, looking for signs of planets around the stars. The working principle of the detector is "transit method".